Method of closing core pin holes



June 20, 1967 T 500K ETAL 3,325,891

METHOD OF CLOSING CORE PIN HOLES Filed Sept. 29, 1964 INVENTOR. 77/0/7/45 A. HUD/x d4 A TTU/F/Vf y DALZ A. [HUI/AN:

United States Patent 3,325,391 METHQD 0F CLOSING CORE PIN HOLES Thomas A. Hook, Irwin, and Daie A. Chovan, Traiford, Pa., assignors to Westinghouse Air Brake Company, Wilmerding, Pa., a corporation of Pennsylvania Filed Sept. 29, 1964, Ser. No. 400,050 2 Claims. (Cl. 29458) This invention relates to a method and means of closing tapered or uniform diameter core pin holes in die castings.

Die castings are made by forcing molten metal under pressure into molds, and often it is necessary that the casting be provided with internal passageways. In order to provide these internal passageways in a die casting, the mold, which is usually made in a plurality of sections, is provided with one or more tapered or uniform diameter core pins for each passageway. Each core pin is integral with and carried by a corresponding section of the mold. When the several sections comprising the mold are assembled, these core pins extend from the inside walls of the mold into the interior thereof to form in the die casting, when molten metal is forced under pressure into the mold, the desired passageways. Subsequent to the cooling and solidifying of the molten metal in the mold, the various sections of the mold may then be disassembled to remove the die casting from the mold. As each section is disassembled, the core pin or pins carried by the respective section are withdrawn from the corresponding core pin holes in the die casting.

The exterior end of each core pin hole in the die casting, subsequent to removal of the casting from its mold, must be closed in some suitable manner to prevent leakage of fluid under pressure from the corresponding passageway in the die casting to the exterior thereof, or if the interior of two intersecting core pin holes are to form two separate interior passageways in the die casting, some suitable means must be used to close communication between the intersecting core pin holes.

Heretofore, one method used to close these core pin holes in a die casting has been to ream the core pin holes to a given diameter and depth, and thereafter drive a pin or cylindrical plug of uniform diameter into the reamed hole, the interior of which has been previously painted with red oxide paint, to close it with a tight fit provided by interference and thereby prevent leakage of fluid under pressure from the passageway within the die casting to the exterior thereof. While the plugging of core pin holes in this manner under some circumstances is satisfactory the reaming operation is costly and time consuming.

Accordingly, it is the general purpose of this invention to provide a novel, simple and relatively inexpensive method and means of closing core pin holes in die castings, subsequent to removal of the casting from the mold in which it was cast, without the necessity for costly reaming operations.

According to the present invention, there is provided a tapered malleable metallic plug having a truncated cone-shaped end which, when the plug is coated with anaerobic sealant and subsequently driven into a core pin hole, either tapered or of uniform diameter formed in a die casting, deforms, and in cooperation with the anaerobic sealant, when hardened in the microscopic depressions in the surfaces of the hole and plug, retains the plug in the hole against removal by vibrational or other forces and prevents leakage of fluid under pressure from the interior of the die casting to the exterior thereof.

In the accompanying drawings:

FIG. 1 is a horizontal cross-sectional view of a typical die casting having a plurality of core pin holes which are ice closed and sealed by tapered plugs embodying the present invention.

FIG. 2 is a cross-sectional view, on an enlarged scale, showing a fragment of the die casting shown in FIG. 1, in which a tapered plug is shown forced in place in a corresponding tapered core pin hole in the die casting.

FIG. 3 is an elevational view, on an enlarged scale, showing details of construction of the tapered plug used in the present invention.

FIG. 4 is a cross-sectional view, on an enlarged scale, showing a fragment of a die casting in which the tapered plug shown in FIG. 3 is shown forced in place in a corresponding core pin hole of uniform diameter in the die casting.

Description FIG. 1 of the drawing shows a portion of a die casting 1 having therein four passageways 2, 3, 4 and 5. These passageways are provided in the die casting 1 by means of tapered core pins. These core pins are removably held in the proper place in a mold into which molten metal is forced under pressure to form the die casting 1 and extend inward to the interior of the mold. The mold is usually made in two or more parts or sections which may be removed, one at a time, subsequent to the molten metal solidifying and cooling. The core pin or pins, which are integral with and extend inward from any section of the mold, are withdrawn from the corresponding core pin hole in the die casting 1 upon removal of the section of the mold from about the casting.

Subsequent to removal of the die casting 1 from the mold in which it was cast, it is necessary that the ex terior end of the tapered core pin holes or passageways 2, 3, 4 and 5 be closed to prevent leakage of fluid under pressure from these passageways to the exterior of the die casting.

According to the invention, the exterior end of each of the four tapered core pin holes in the die casting 1, shown in FIG. 1 of the drawing, is closed by a tapered plug 6, constructed as shown in FIG. 3, of suitable malleable metal, such as aluminum or aluminum alloy. As shown in FIG. 3, the tapered plug 6 comprises a first inverted truncated cone-shaped portion 7, the diameter of the larger end of which is indicated in FIG. 3 by the letter A, and the length of which is indicated by the letter H. This diameter A should be slightly less, for example, .003 inch, than the nominal diameter of the outer end of the corresponding tapered core pin hole, since the diameter of the outer end of the core pin hole may vary and be as much as .005 inch greater than or .005 inch less than the nominal diameter. The length H of the inverted cone-shaped portion 7 may vary, for example, from .250 inch to .300 inch.

The angle formed between the altitude and slant height of the truncated cone portion 7 is small, and may vary, for example, from 2 54' to 3 48. This angle is indicated by the letter X in FIG. 3 and should be greater than the angle of taper of the corresponding core pin hole in order to provide, when the plug 6 is inserted into the tapered core pin hole, an annular chamber, indicated in FIG. 2 of the drawing by the numeral 8, between the outside surface of the truncated portion 7 and the wall surface of the tapered core pin hole.

Formed integral with the lower end of the inverted cone-shaped portion 7 is a second inverted truncated cone portion 10, having at its larger diameter end a short flat surface or cylindrical portion 9, the diameter of which is indicated by the letter B in FIG. 3 and is only slightly, for example, from .001 inch to .003 inch, less than the diameter of the outer or larger end of the corresponding tapered core pin hold that is to be closed by the plug 6. Furthermore, the diameter of the short cylindrical portion 9 must be greater than the diameter of the corresponding tapered core pin hole at a distance from the top of the tapered core pin hole in the die casting equal to the height H of the first inverted cone-shaped portion 7 by, for example, .003 inch. The angle of taper formed between the length or altitude and slant height of the truncated cone portion may be, for example, This angle is indicated in FIG. 3 'by the letter Y.

In order to illustrate the proper dimensions of plugs for closing the open end of both tapered and uniform diameter core pin holes of different sizes, the following table is given by way of example, it being understood that the letters in the table refer to the corresponding letters in FIG. 3 of the drawings.

of fluid under pressure from within a die casting to the exterior thereof.

FIG. 4 of thedrawings shows a fragment of a die casting 11 having a core pin 12 of uniform diameter closed by a tapered plug, such as the tapered plug 6' Uniform Tapered Diameter Gore Pin Core Pin Hole Size A (inch) B (inch) C (inch) D (inch) E (inch) F (inch) G (inch) H (inch) X (deg) Y (dog) Hole Size, (Outer End),

(inch) (inch) When using a plug 6 to close the open end of a tapered core pin hole, a plug is selected from the above table, the dimensions of which correspond to the diameter of the outer end of the tapered core pin hole to be closed by the plug.

The selected plug is first coated with a suitable anaer obic sealant, available commercially.

Next, the inverted truncated cone portion 10 of the plug is inserted in the open outer end of the tapered core pin hole in the die casting 1 that is to be closed by the plug.

Thereafter, a force is applied to the upper end of the truncated portion 7 of the plug 6, as by tapping with a hammer, to force the plug 6 downwardly until it occupies the position shown in FIG. 2 in which the upper end of the truncated cone portion 7 is flush with the top of the die casting 1. Since the plug 6 is made of a malleable metal, the periphery of the short cylindrical portion 9 and the upper outer edge of the inverted truncated cone portion 10 of the plug 6 will be deformed or bent .upward into the chamber 8 as the plug 6 is forced downward to the position shown in FIG. 2 due to the taper in the core pin hole. Furthermore, as the result of this upward bending, the remainder of the chamber 8 will be filled and compacted with the anaerobic sealant with which the outer surface of the plug 6 was coated prior to inserting the inverted truncated cone-shaped portion 10 into the open end of the tapered core pin hole.

The anaerobic sealant, which now fills the chamber 8, has the characteristic of automatically hardening, when once confined between close-fitting metal parts where it lacks contact with the atmosphere, into a tough solid in a few hours at room temperature. The surface roughness of the metal parts, plug '6 and die casting 1, provides anchors for the hardened anaerobic sealant. Thus, the plug 6 is keyed to the inside wall surface of the tapered core pin hole to prevent relative movement between the plug 6 and the die casting 1. Consequently, after the anaerobic sealant in the chamber 8 has hardened, the plug 6 cannot be removed from the core pin hole into which it was previously driven. Furthermore, the hardened anaerobic sealant, together with the inwardly bent, short cylindrical portion 9 and inverted truncated cone-shaped portion 10, prevents leakage of fluid under pressure from the corresponding passageway within the die casting 1 past the plug 6 to the exterior thereof. Thus, the plug 6, when coated with an anaerobic sealant and subsequently driven into the open end of a tapered core pin hole, provides a simple, low cost, and effective means of closing the open end of the core pin hole and preventing leakage The selected plug is first coated with a suitable anaerobic sealant, available commercially.

Next, the inverted cone portion 10 of the plug is inserted in the open outer end of the core pin hole 12 of uniform diameter in the die casting 11.

Thereafter, a force is applied to the upper end of the truncated cone portion 7 of the plug, as by tapping with a hammer, to force the plug downwardly until it occupies the position shown in FIG. 4, in which the upper end of the truncated cone portion 7 is flush with the top of the die casting 11.

As hereinbefore explained, the periphery of the short cylindrical portion 9 and the upper outer edge of the inverted truncated cone portion 10 of the plug will be deformed or bent upwardly as the plug is forced downwardly, since it will be understood that the diameter of the larger diameter end of the inverted truncated cone portion 10 of the plug selected to close the core pin hole 12 is greater than the uniform diameter of this core pin hole.

Furthermore, it will be understood that a chamber 13, which corresponds to the chamber 8 shown in FIG. 2, is likewise filled and compacted with the anaerobic sealant which hardens into a tough solid to key the plug to the inside wall surface of the core pin hole 12 to prevent relative movement between the plug and the die casting 11. Consequently, after the anaerobic sealant in the chamber 13 has hardened, the plug cannot be removed from the core pin hole 12 of uniform diameter for the same reasons that the plug shown in FIG. 2 cannot be removed from its corresponding tapered core pin hole. Accordingly, it is apparent that the plug provided by the present invention is equally suitable for closing tapered core pin holes or core pin holes of uniform diameter.

Having now described the invention, what we claim as new and desire to secure by Letters Patent is:

1. The method of closing a core pin hole in a casting comprising the steps of:

(a) providing a malleable metallic plug having two truncated cone portions joined in tandem relationship with the larged diameter end of one of said two truncated cone portions adjacent the smaller diameter end of the other of said two truncated cone portions,

(b) coating the outer surface of said tapered malleable metallic plug with an anaerobic sealant,

(c) inserting the smaller diameter end of said one truncated cone portion into the outer end of the core pin hole to be closed, and

(d) forcing said plug into the core pin hole until the exterior end of said plug is flush with the exterior surface of the casting surrounding the core pin hole,

(e) the flexing of the larger diameter end of said one trucated cone portion insuring compacting of the sealant in the core pin hole between the larger diameter ends of the two truncated cone portions.

2. The method of closing a core pin hole in a casting comprising the steps of:

(a) providing a tapered malleable metallic plug having two truncated cone portions joined in tandem relationship with the larger diameter end of one of said two truncated cone portions adjacent the smaller diameter end of the other of said two truncated cone portions,

(b) coating the outer surface of said tapered malleable metallic plug with an anaerobic sealant,

(c) inserting the smaller diameter end of said one truncated cone portion into the outer end of the core pin hole to be closed, and

(d) forcing said plug into the core pin hole until the exterior end of said plug is flush with the exterior surface of the casting surrounding the core pin hole,

(e) the flexing of the larger diameter end of said one References Cited UNITED STATES PATENTS 2,283,672 5/1942 Frances 138-89 2,795,844 6/1957 Liszak 29-458 2,821,323 1/1958 Lee 220-24 2,886,203 5/ 1959 6011 220-24 2,951,506 9/ 1960 Diperstein 29-402 X JOHN F. CAMPBELL, Primary Examiner. T. H, EAGER, Assistant Examiner. 

1. THE METHOD OF CLOSING A CORE PIN HOLE IN A CASTING COMPRISING THE STEPS OF: (A) PROVIDING A MALLEABLE METALLIC PLUG HAVING TWO TRUNCATED CONE PORTIONS JOINED IN TANDEM RELATIONSHIP WITH THE LARGED DIAMETER END OF ONE OF SAID TWO TRUNCATED CONE PORTIONS ADJACENT THE SMALLER DIAMETER END OF THE OTHER OF SAID TWO TRUNCATED CONE PORTIONS, (B) COATING THE OUTER SURFACE OF SAID TAPERED MALLEABLE METALLIC PLUG WITH AN ANAEROBIC SEALANT, (C) INSERTING THE SMALLER DIAMETER END OF SAID ONE TRUNCATED CONE PORTION INTO THE OUTER END OF THE CORE PIN HOLE TO BE CLOSED, AND (D) FORCING SAID PLUG INTO THE CORE PIN HOLE UNTIL THE EXTERIOR END OF SAID PLUG IS FLUSH WITH THE EXTERIOR SURFACE OF THE CASTING SURROUNDING THE CORE PIN HOLE, (E) THE FLEXING OF THE LARGER DIAMETER END OF SAID ONE TRUCATED CONE PORTION INSURING COMPACTING OF THE SEALANT IN THE CORE PIN HOLE BETWEEN THE LARGER DIAMETER ENDS OF THE TWO TRUNCATED CONE PORTIONS. 